Exposure method, exposure apparatus, and device manufacturing method

Abstract

Provided is an exposure method that includes setting a first exposure condition so as to calculate a coefficient for predicting the fluctuation in the imaging characteristics of the projection optical system under a certain exposure condition; determining the coefficient and a permissible value calculated from aberration measurement reproducibility based on a fluctuation characteristic model; calculating a predicted amount of the fluctuation in the imaging characteristics under the first exposure condition based on the coefficient; determining whether or not the predicted amount is less than the permissible value for each time instant; and starting calculation of the predicted amount of the fluctuation in the imaging characteristics under a second exposure condition at the time at which it is determined by the determining that the predicted amount is less than the permissible value.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to an exposure method and an exposure apparatus, and a device manufacturing method.[0003]2. Description of the Related Art[0004]An exposure apparatus is an apparatus that transfers a pattern of an original (reticle or the like) onto a photosensitive substrate (e.g., wafer or the like where the surface thereof is coated with a resist layer) via a projection optical system in a lithography step included in manufacturing steps for a semiconductor device, a liquid crystal display device, and the like. One of the important optical characteristics of such an exposure apparatus is alignment accuracy with which the patterns in a plurality of steps are overlaid accurately. An important factor that influences the alignment accuracy includes a magnification error of the projection optical system. The required pattern size shrinks every year, and accordingly a requirement for an improvement in alignmen...

AI Technical Summary

Benefits of technology

[0007]The present invention provides an exposure method that is advantageous for predicting the fluctuation in the imaging characteristics for each exposure condition in a short time with high accuracy.

Problems solved by technology

An important factor that influences the alignment accuracy includes a magnification error of the projection optical system.

Here, it is known that, when the projection optical system absorbs a part of the exposure energy, a heat generated by the absorption changes the temperature of the projection optical system, resulting in change in the optical characteristics such as the refractive index of the projection optical system, that is, resulting in occurrence of so-called thermal aberration (exposure aberration).

Consequently, non-negligible measurement errors may undesirably occur during alignment measurement.

Consequently, it becomes difficult to determine the aberration fluctuation coefficient under the second exposure condition with high accuracy.

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